1. Technical Field
The disclosure relates to an imaging unit provided at a distal end of an insertion unit of an endoscope that is configured to be inserted into a subject for capturing an image of an inside the subject, and relates to an endoscope apparatus.
2. Related Art
In medical and industrial fields, endoscope apparatuses have conventionally been used widely in a variety of examinations. Among these endoscope apparatuses, a medical endoscope apparatus has been used widely since it is capable of obtaining an in-vivo image inside a body cavity without incising the subject by inserting a flexible insertion unit, which has an elongated shape and is provided with an imaging element at a distal end thereof, inside the body cavity of the subject such as a patient, and furthermore, it is capable of performing a therapeutic treatment as necessary by protruding a treatment tool from the distal end of the insertion unit.
An imaging unit including an imaging element and a lens unit that performs image-formation of a subject image on a light-receiving surface of the imaging element (for example, see JP 2005-304876 A) are fitted to the distal end of the insertion unit of such endoscope apparatus.
FIG. 11 is a schematic view illustrating a conventional imaging unit. In FIG. 11, the imaging unit is viewed in a direction orthogonal to an optical axis direction and orthogonal to a stacking direction of a multi-layer substrate. As illustrated in FIG. 11, a conventional imaging unit 140 has a configuration in which a substrate 145 extends in the optical axis direction from an imaging element 144. The imaging element 144 has a light-receiving surface covered with a glass lid 149. The substrate 145 is electrically connected to the imaging element 144 by an inner lead, which is not illustrated, and a connected part thereof is sealed with an adhesive 154a. A multi-layer substrate 146 is formed on the substrate 145, and a distal end of a signal cable 148 is connected to a proximal end portion of the multi-layer substrate 146.
In an endoscope apparatus, accompanied with forward and backward operation of an insertion unit as well as a bending movement thereof for adjusting a camera angle during use of an endoscope, a force pushing in a distal end direction or a force shaking up and down and twisting is applied to the signal cable 148. This causes an upward or downward stress on the substrate 145 and the multi-layer substrate 146 to which the signal cable 148 is connected. Accordingly, as illustrated in FIGS. 12A and 12B, a central part Sp of the substrate 145 and the multi-layer substrate 146 may be bent. In an imaging unit of the endoscope, a central part of the substrate may be warped by heat and a load during manufacturing of the imaging unit. In the endoscope apparatus, a compact imaging unit has been promoted to reduce a diameter of the insertion unit; however, as the imaging unit becomes smaller, an influence of this bending stress becomes non-negligible, whereby performance of the imaging unit may be degraded.